1. Field of the Invention.
The present invention is in the field of improved polyamide compositions. More particularly, this invention is in the field of nylon compositions for molding and extruding, both with and without reinforcement, and for use as film.
2. Description of the Prior Art.
Polyamides, sometimes known broadly as nylon compositions, have long been used in molding applications requiring stiffness, impact toughness, and good strength characteristics; in these applications, the plastic material is used both as is, and with various kinds of reinforcement; examples of such compositions are disclosed in U.S. Pat. No. 4,495,324. Polyamides have also been used widely in a film form for packaging in food, medical and industrial applications. Polyamides are useful as film due to their chemical resistance, toughness, strength, aroma flavor retention, and gas-barrier characteristics.
In certain molding applications, reinforcement of the resin with fiberglass improves properties such as stiffness, notched-Izod impact values, and tensile strength. It is desireable to attain these improvements while at the same time attaining a balance in other properties such as ultimate elongation and drop weight impact strength.
In certain film uses, the ability of a polyamide film to drape or conform to a particular shape is a desirable characteristic which is not easily achieved, due to the stiffness of the polyamide composition. It is necessary to modify this stiffness. In addition, films now known in the art have a tendency to stiffen upon exposure to heat, hindering their utility in applications such as vacuum forming. Plasticizers of various natures have been used in attempts to provide good film properties, but the addition of a low-molecular-weight plasticizer can lead to its plating out on chill rolls, exuding from, and therefore embrittling, the film over time, and otherwise detracting from the efficacious use of the film.